Countersinking tool



Sept. 26, 1961 H. 1 BERGERON COUNTERSINKING TOOL Filed Aug. 11, 1958 FIG.

INVENTOR, BERGERON- QHARRY BY MM EM 0 9 ATTORNEY nite This invention relates to an improvement in countersinking device and deals particularly with a simple and effective apparatus for providing smooth countersunk openings in wood or similar material.

In making countersunk apertures in wood, or even in harder materials such as metal and the like, it is common practice to use a generally conically shaped countersinking tool having radially spaced teeth extending longitudinally of the conical surface. While such devices have been used successfully for many years, they do not produce an extremely smooth tapered surface in wood or similar materials. This is particularly true in using wood which has a tendency to split or splinter and the use of such tools often results in a somewhat uneven surface with splinters of wood removed from the surface of the wood adjoining the opening being countersunk.

Another difiiculty in the use of countersinking tools of usual design lies in the fact that the teeth or ribs of the tool have a tendency to collect the material being cut thus filling some or all of the teeth and impairing the cutting operation. As a result, with many materials, it is often necessary to stop rotation of the countersinking tool at frequent intervals to clean the tool so that it will function properly. It is an object of the present invention to provide a countersinking device which avoids these previous difiiculties.

A feature of the present invention resides in the provision of a countersinking tool including a hollow shank having a counter-sinking head thereupon provided with a substantially frusto-conical surface. Apertures are formed through this frusto-conical surface extending from the exterior surface to the interior of the tubular body. The edges of these apertures form cutting edges which engage the material to be countersunk during the rotation of the tool to produce the countersunk opening. The material which is cut away during the countersinking operation is directed to the interior of the tool so as not to interfere with the cutting action. In other words, the waste material is directed to the interior of the tool and accordingly does not tend to collect on the cutting edges.

A feature of the present invention resides in the provision of a device of the type described having a series of angularly spaced apertures leading from the frusto-conical outer surface to the interior of the tool so that one edge of each of the apertures extends substantially tangent to the inner wall of the tubular body. The tool is rotated so that the tangential edge of the apertures forms the cutting edge of the device. As a result, the waste material which is cut away is guided smoothly into the interior of the body more effectively than would be possible in the event the apertures were formed radially from the axis of rotation.

A further feature of the present invention resides in the provision of a device of the type described in which the waste material is guided toward the periphery of the inner wall of the tool so that this material may be guided along a circular or spiral path to be ejected from an open end of the tool.

These and other objects and novel features of the present invention will be more clearly and fully set forth in the following specification and claims:

In the drawings forming a part of the specification:

FIGURE 1 is a side elevational view of the countersinking tool.

Patent 6 assists Patented Sept. 26, I961 FIGURE 2 is a longitudinal sectional view through the tool illustrated in FIGURE 1.

FIGURE 3 is an enlarged cross sectional view through the tool, the position of the section being indicated by the line 3-3 of FIGURE 1.

FIGURE 4 is a bottom plan view of the tool.

The countersinking tool is indicated in general by the letter A. The tool includes a hollow cylindrical shank It) having a cutting head 11 located intermediate its ends. The upper end 12 of the shank 10 is preferably of suitable diameter to fit into a drill chuck or the like and has a relatively small diameter passage 13 extending therethrough. The lower end of the tool is also cylindrical and is preferably of proper diameter to fit within the hole to be countersunk; and is provided with a. passage 15 extending therethrough. The passages 13 and 15 are axially aligned and are connected by a shoulder 16 located inwardly of the cutting head 11 where these passages are of different diameters.

The cutting head llincludes a relatively large diameter portion 17 communicating at its lower end with a frustoconical surface 19 which is designed to provide the proper angle for the taper of the countersunk opening. The upper edge of the large diameter cylindrical portion 17 is connected by a frusto-conical portion 22 to a cylindrical portion 23 which is of smaller diameter than the portion 17 but which, in the form illustrated, is of larger diameter than the upper portion 12 of the shank. This short cylindrical portion 23 is connected by a frusto-conical portion 24 to the upper cylindrical portion 12.

The passage 15 in the lower end of the tool forms a chamber 25 designed to receive Waste material which has been cut from the material being countersunk. A series of angularly spaced apertures 26 are arranged with their axes on a substantially common plane normal to the axis of rotation of the tool. As is best shown in FIGURES 3 and 4 of the drawings, each of the apertures 26 is arranged with its outer edge 27, which is the trailing edge during rotation, substantially tangent to the inner surface of the passage 15 through the lower portion of the tool. This outer edge 27, at its juncture with the frusto-conical surface 19, forms the cutting edge designed to cut into the material being countersunk and to guide the material being cut through the corresponding aperture 26 into the chamber 25 defined by the cylindrical inner wall 15.

As a result of this arrangement, the waste material Which is cut by each cutting edge enters a corresponding aperture 26 and is pushed inwardly by the pressure of additional material being cut. Due to the fact that the outer surface of each aperture is substantially tangent to the wall of the chamber 25, the waste material has a tendency to move in a circular or spiral path once it enters the body of the tool so that it can drop from the lower open end of the tool without clogging or binding.

The countersinking tool described provides a very smoothly surfaced countersunk opening, particularly in a material such as wood which has a tendency to compress slightly during the countersinking operation. Actually, the outer surface of the frust-o-conical portion 19 has no outwardly projecting teeth and as a result, the finished surface is substantially the same shape as the frusto-conical surface 19 itself. As a result, there is no chattering of the tool during operation and only small particles of the waste material are cut away during each rotation of the tool. It is presumed that as downward pressure is exerted upon the tool during its rotation, the frusto-conical sur face has a tendency to compress the wood and as each aperture 26 revolves, the material being countersunk expands slightly into the outer end of the aperture and is cut off by the rear cutting edge of the aperture. This is augmented by the undercut grooves 30 between apertures. In spite of the fact that there are no projecting teeth to clog up, the counter-sinking tool seemed to work as quickly as countersinking tools of the conventional type but with a much smoother action. As a result, countersunk openings may be formed in the surfaces of wood and similar material which has a distinct tendency to splinter to produce a smooth finished surface which cannot be readily obtained with any other countersinking tool with which I am familiar.

As indicated in FIGURE 3 of the drawings, the surface of the frusto-conical portion 19 is grooved between the apertures 26 with grooves of gradually increasing depth from the trailing or cutting edge 27 of each aperture to the leading edge 29 of the next adjacent aperturein the direction of rotation. These grooves are indicated by the numeral 30, and are so arranged that the trailing edge of each aperture 26 projects slightly beyond the leading edge thereof, to perform the cutting operation.

In accordance with the patent statutes, I have described the principles of construction and operation of my improvement in countersiuking device, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. A countersinking tool including an elongated shank, a head on said shank having an axial aperture extending therethrough from the lower end thereof, a frusto-conical surface on the undersurface of said head having a series of angulariy spaced apertures therethrough communicating with said axial aperture, and grooves in said frustoconical surface between said angularly spaced apertures, said grooves gradually increasing in depth from the trailing edges of said angularly spaced apertures to the leading edge of the next angularly spaced aperture.

2. The structure of claim 1 and in which the trailing edge of each aperture is substantially tangent to the wall of said axial aperture.

References Cited in the file of this patent UNITED STATES PATENTS 1,586,559 Lau rsen June 1, 1926 2,829,544 Bergstrom Apr. 8, 1958 FOREIGN PATENTS 258,918 Switzerland May 16, 1949 568,265 Germany Jan. 17, 1933 

